Holding device for a twin pressure roller of a drafting unit

ABSTRACT

A holding device for a twin pressure roller of a drafting unit includes a number of bottom rollers. The twin pressure roller includes a stationary axle and two rotatably supported upper rollers. The holding device includes at least one positioning element assigned to the axle of the twin pressure roller and at least one force transmission element, wherein the positioning element is arranged in the area of the center of the axle of the twin pressure roller and thus permits the twin pressure roller to move in a pendulum fashion around the center. The holding device, together with the twin pressure roller may be lifted from the bottom roller. At least one catch bearing for approximate positioning during placement on the bottom rollers is assigned to the twin pressure roller. It may further be provided that the force transmission element is arranged separately from the positioning element and that the catch bearing is integrated into the force transmission element.

BACKGROUND AND SUMMARY OF THE INVENTION

This application claims the priority of German Application No. 10 2005027 194.4, filed Jun. 6, 2005, the disclosure of which is expresslyincorporated by reference herein.

The present invention relates to a holding device for a twin pressureroller of a drafting unit comprising a number of bottom rollers, thetwin pressure roller comprising a stationary axle and two rotatablysupported upper rollers, the holding device comprising at least onepositioning element assigned to the axle of the twin pressure roller andat least one force transmission element, whereby the positioning elementis arranged in the area of the center of the axle of the twin pressureroller and thus permits the twin pressure roller to move in pendulumfashion around the center and whereby the holding device, together withthe twin pressure roller, can be lifted from the bottom roller.

A holding device of the above mentioned type is prior art in Germanpublished patent application 38 23 872. In the case of the known holdingdevice, the twin pressure roller is held in the center of its axle byuse of a positioning element and positioned in relation to therespective bottom roller. The positioning element is adjustable in fibertransport direction and permits the adjustment of a so-called recess oroverhang of the upper rollers. The rotational axis of the upper rollersin relation to the fiber transport direction are arranged to therotational axis of the bottom rollers either somewhat forwards orbackwards out-of-line. The axle of the twin pressure roller is taken upin the positioning element in such a way that moving in pendulum fashionaround the center is permitted. Because of this permitted moving inpendulum fashion in connection with an overhang or recess, the twinpressure roller is aligned parallel to the bottom roller when pressedthereon.

An exact parallelism of the twin pressure roller to the bottom rollersis important in order that an even drafting of the fiber strand can takeplace. When an upper roller is not aligned parallel to its respectivebottom roller, then the nipping of the fiber strand over the width ofthe roller is different and thus the fiber strand will be draftedunevenly.

The force transmission of a pressing force for the loading of the upperrollers takes place integrated in the positioning element in the centerof the axle of the twin pressure roller.

The known holding device has proved itself well in practice in draftingunits having a relatively small gauge, for example, in the case ofdrafting units for ring spinning machines. After the twin pressureroller is raised from the bottom rollers, which action may, for example,be necessary for the purposes of eliminating a fault, the upper rollers,when replaced on the bottom rollers, automatically find their positionin the set overhang or recess, and the twin pressure roller, due to thepermitted movement in pendulum fashion, aligns itself again exactly tothe bottom roller. The holding device with the positioning element doesnot need to be aligned parallel to the bottom rollers. This a crucialadvantage, as for the purposes of fixing and loading the holding deviceby the use of the pressure force, usually a large number of componentsare applied, in the case of which, because of the addition of individualtolerances, good parallelism of the positioning element with the bottomrollers cannot be guaranteed.

In the case of an increased gauge of over 100 mm it can however easilyoccur that even a small oscillation angle will result in such a largemisalignment of one upper roller of the twin pressure roller to theother upper roller that one upper roller is placed with an overhang,while the other upper roller of the twin pressure roller is placed witha recess to the bottom roller. In particular, in the case of draftingunits for air spinning machines, which have a large gauge of 200 mm andover, these known holding devices are no longer reliable in theirapplication. When the twin pressure roller is replaced after beingraised, the upper rollers do not find their set position, as theoscillation angle cannot be limited by the positioning element to suchan extent that placing one upper roller with a overhang and the otherroller with a recess can be prevented in the long run.

A drafting unit with a large gauge is known in German published patentapplication 39 07 745, in which the twin pressure roller is positionedand loaded by way of two holding devices in close proximity to bothupper rollers. In the case of this configuration, a false positioning ofthe upper rollers onto the bottom rollers is prevented; however, amovement in pendulum fashion of the twin pressure roller is notpossible, so that the twin pressure roller cannot align itself parallelto the bottom roller. Rather, both holding devices must be absolutelyexactly aligned to the bottom roller, so that both upper rollers of thetwin pressure roller are also in the correct position. This cannot bealways ensured, despite complicated adjustment work.

It is an object of the present invention to improve the known holdingdevice and to permit movement in a pendulum fashion of the twin pressureroller also in the case of drafting units with a large gauge, withoutpermitting a false positioning of the upper rollers when the twinpressure roller is replaced on the bottom roller.

This object has been achieved in accordance with the present inventionin that at least one catch bearing is assigned to the twin pressureroller for approximate positioning of the twin pressure roller whenplaced onto the bottom rollers.

By providing at least one catch bearing, the capacity of the twinpressure roller to move in pendulum fashion may be adjusted in the longrun in such a way, that when the twin pressure roller is placed on thebottom rollers, a false positioning of both upper rollers is excludedand that despite this, when the pressure force is applied, a parallelalignment of the twin pressure roller to the bottom rollers can takeplace. The catch bearings act thereby at least shortly before thereplacing of the twin pressure roller and secure advantageously anapproximate parallel alignment of the twin pressure roller to such anextent that the upper rollers of the twin pressure roller, depending onthe chosen adjustment, are either both placed on the bottom rollers withan overhang or both with a recess. The capacity to move in pendulumfashion provided within the approximate parallel alignment permits thetwin pressure roller, when the pressure force is applied, to alignitself exactly parallel to the bottom rollers. Placement of one upperroller with overhang and the other upper roller with recess is thuseffectively prevented.

The catch bearing may be designed in different ways. Advantageously, itacts from the center of the axle at the greatest possible distances onthe twin pressure roller. The further the catch bearing is arranged fromthe center of the axle of the twin pressure roller, which represents thefulcrum in the pendulum movement, the easier the rather contradictoryfunctions of the catch bearing are reliably realized. On the one hand,the catch bearing should limit the oscillation movement of the twinpressure roller to such an extent that a false positioning of the upperrollers is prevented, on the other hand, however, there must besufficiently large oscillation capacity, so that an exact parallelalignment under the action of the pressure force is permitted. The catchbearing is therefore designed in such a way that it guides the twinpressure roller to the point of placement on the bottom rollers, butthen does not hinder the twin pressure roller in their oscillatingalignment parallel to the bottom rollers.

The catch bearing may be assigned to an upper roller of the twinpressure roller, it acts, however, particularly advantageously on theaxle of the twin pressure roller, as this does not begin to rotate whenthe twin pressure roller is placed on the bottom roller. In anadvantageous embodiment of the present invention, it is provided whentwo catch bearings are arranged at a distance to one another in closeproximity to the upper rollers. A symmetrical embodiment of thecomponents, especially of the holding device, is thus permitted in asimple way. It is further advantageous when the force transmissionelement, which transmits the pressure force for the upper rollers to theaxle of the twin pressure roller, is integrated in the positioningelement. The force transmission thus takes place together with thepositioning in the center of the axle of the twin pressure roller, andthe force is distributed evenly on both upper rollers.

Depending on the required pressing force in ratio to the chosen diameterof the axle of the twin pressure roller, a very high bowing of the axleunder load can occur if the force transmission element is arranged inthe center of the axle. This bowing under load results in a slanting ofthe two upper rollers and a deviation from the parallel position. Inorder to avoid too great a deflection of the axle it is advantageous toarrange the force transmission element separately from the positioningelement. Particularly advantageous is the configuration of at least twoforce transmission elements each in close proximity to the upperrollers. It must be heeded, however, that no coerced positioning due tothe force transmission elements takes place which would hinder theoscillating alignment of the twin pressure roller.

In the case of the force transmission element separated from thepositioning element, it can be advantageous to integrate the catchbearing in the force transmission element, in order to permit both toact in close proximity to the upper rollers on the axle of the twinpressure roller.

The catch bearing advantageously has a fork-like design and prevents thetwin pressure roller from advancing too far out of its position when itis raised from the bottom roller.

BRIEF DESCRIPTION OF THE DRAWINGS

These and further objects, features and advantages of the presentinvention will become more readily apparent from the following detaileddescription thereof when taken in conjunction with the accompanyingdrawings wherein:

FIG. 1 shows a partly intersectional side view of a partly showndrafting unit including holding devices for twin pressure roller;

FIG. 2 shows a view of a holding device for a twin pressure roller alongthe intersectional surface II-II of FIG. 1; and

FIG. 3 shows a view of a holding device for a twin pressure roller alongthe intersectional surface III-III of FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS

The drafting unit 1 partly shown in FIG. 1 includes a number of rollerpairs 2, 3 and 4, 5, which transport a fiber strand 6 in fiber transportdirection A through the drafting unit 1 and draft it to the desireddegree of fineness. Guiding belts 7, 8 are assigned in the known way tothe roller pair 4, 5. It can be provided that the drafting unit 1includes further roller pairs, arranged upstream of the roller pair 4, 5or downstream of the roller pair 2, 3. The fiber strand 6, drafted tothe desired degree of fineness, is fed subsequently to a twist device ofchoice downstream of the drafting unit, for example an airjetarrangement, where the fiber strand 6 receives its spinning twist. Theupper rollers 3 and 5 are positioned in relation to the driveable bottomrollers 2 and 4 and pressed by way of two holding devices 9. The upperrollers 3 and 5 themselves are hereby not driven, but rather are takenalong by the motion of the bottom rollers 2, 4.

The holding device 9 is loaded with a pressing force F by way of loadingdevices (not shown) in the known and optional way, which holding device9 can be raised together with the upper rollers 3 and 5 from the bottomrollers 2 and 4. The pressing force F can be applied by pneumatic ormagnetic force generating elements or by means of metal springs.

As can be seen in FIG. 3, the upper rollers 3 of two adjacent spinningpositions are combined by a joint axle 10 to form a twin pressure roller11. Both bottom rollers 2 of these adjacent spinning positions canhereby be individual bottom rollers having separate drives. They canalso be just as well designed as a continuous bottom cylinder extendingin machine longitudinal direction in the way denoted by the broken line.

According to FIG. 1, the upper rollers 3, 5 are arranged in relation tothe respective bottom roller 2, 4 with a slight overhang or recess. Thearrangement of the upper roller 5 to the bottom roller 4 is denoted asrecess when the upper roller 5, as seen in transport direction A, isarranged somewhat further upstream than the bottom roller 4. The rollerpair 2, 3 shows an overhang of the upper roller 3, in which the upperroller 3 in the fiber transport direction A is arranged downstream ofthe bottom roller 2.

FIG. 2 shows a top view onto the roller pair 2, 3, whereby the holdingdevice 9 is intersected along the intersectional surface II-II ofFIG. 1. In the area of the center 12 of the axle 10 of the twin pressureroller 11, a positioning element 13, contained in the holding device 9,is provided. The positioning element 13 has a positioning surface 14,which acts together with the axle 10 and ensures the positioning of thetwin pressure roller 11 with the desired overhang in relation to thebottom rollers 2. The positioning surfaces 14 have hereby a clearancefit with the axle 10, so that the twin pressure roller 11 can execute amovement like a pendulum in arrow directions B and C around the center12. The capacity to move in pendulum fashion in arrow direction B and Cin connection with the adjusted overhang or recess effects aself-regulatory alignment of the twin pressure roller parallel to thebottom rollers 2. An uneven nipping of the fiber strand 6, caused by aslanting of the upper roller 3 in relation to the bottom roller 2, andthe consequent uneven drafting thereof is hereby avoided. Thepositioning surface 14 can hereby be designed slightly convex.

The larger the gauge E of the drafting unit 1 is, the larger the swiveldistance which the upper roller 3 executes along the fiber transportdirection A with the same oscillation angle of the axle 10 around thecenter 12. In the case of drafting units having a large gauge E of over100 mm, as are applied as standard in airjet spinning machines, theoscillation motion of the twin pressure roller 11 becomes so large thatwhen the twin pressure roller 11, having been raised from the bottomrollers 2 in order to eliminate a fault in the spinning process, arereplaced on the bottom rollers 2, a faulty positioning of the twinpressure roller 11 can occur. It may happen that the axle 10 of the twinpressure roller 11 inclines to such an extent that one upper roller 3with an overhang and the other upper roller 3 with a recess are disposedon the respective bottom rollers 2. This configuration renders thespinning process impossible. It is therefore provided that at least onecatch bearing 15 is assigned to the twin pressure roller 11. The catchbearing 15 serves to approximately position the twin pressure roller 11when being replaced on the bottom rollers 2 and to prevent faultypositioning of the twin pressure roller 11. The catch bearing 15 canhereby be arranged to the axle 10 of the twin pressure roller 11. Thecatch bearing 15 includes at least one catch surface 16, which limitsthe twin pressure roller 11 in its oscillation motion in direction B orC as soon as the oscillation angle exceeds a certain size. The catchbearing 15 is preferably arranged as far from the center 12 of the twinpressure roller 11 as possible. The catch surfaces 16 are therebyarranged at such a distance from the axle 10 of the twin pressure roller11, that the surfaces 16 prevent a faulty placement of the twin pressureroller 11 on the bottom rollers 2, while not hindering the movement inpendulum fashion for the parallel alignment of the twin pressure roller11. This aim can be more easily achieved the further away the catchbearing 15 is from the center 12.

The pressing force F must be transmitted through the holding device 9into the axle 10 of the twin pressure roller. This can occur in that aforce transmission element is integrated into the positioning element13. In this embodiment (not shown), the pressing force F is distributedthrough the axle 10 onto both of the upper rollers 3 of the twinpressure roller 11. In the case of the drafting unit shown here having alarge gauge E and having, in comparison thereto, a relatively smalldiameter D of the axle 10 of the twin pressure roller 11, the bowingunder load of the axle 10 can, depending on the strength of the pressingforce F, be so great that a slanted position of the upper rollers 3 dueto the deforming occurs, which then in turn impairs the evenness of thedrafted fiber strand. In the case of drafting units 1 for airjetspinning machines, the diameter D of the axle 10 is often less than atenth of the gauge E. In order to avoid the unfavorably high deflection,it is advantageous to arrange force transmission elements 17, as shownin FIG. 3, separately from the positioning elements 13. The forcetransmission element is hereby arranged as closely as possible to theupper roller 3 and transmits the pressing force F from the holdingdevice 9 through the pressing surfaces 18 onto the axle 10. Thedeflection of the axle 10 can thus be minimized. The pressing surfaces18 are advantageously designed as even surfaces, which transmit thepressing force F onto the axle 10, without influencing the position ofthe axle 10 and without forcing the twin pressure roller into a positionwhich may be false.

In an advantageous embodiment of the present invention, the catchbearing 15 is integrated into the force transmission element 17. Theintegrated component can be advantageously fork-like in design, in whichthe fork base comprises the pressure surfaces 18 and the lateralsurfaces of the fork comprise the catch surfaces 16.

In the embodiment according to FIG. 3, in which the force transmissionelement 17 is arranged separated from the positioning element 13, it isimportant that the holding device 9 comprises a gap 19 in thepositioning element 13, so that no force can be transmitted to thecenter 12 of the axle 10. In this embodiment, depending on the loadingaggregate used, it can be advantageous to provide two pressing forcesF′, denoted by a broken arrow, exactly on the force transmissionelements 17, instead of one applied pressing force F in the center 12.

The upper roller 5 with the guiding belt 8 can, of course, be alsodesigned, identical to the above described upper roller 3, as twinpressure roller 11, which is positioned in the same manner by way of aholding device 9 and loaded with a pressing force F.

The foregoing disclosure has been set forth merely to illustrate theinvention and is not intended to be limiting. Since modifications of thedisclosed embodiments incorporating the spirit and substance of theinvention may occur to persons skilled in the art, the invention shouldbe construed to include everything within the scope of the appendedclaims and equivalents thereof.

1. A holding device for a twin pressure roller of a drafting unitincluding a number of bottom rollers, the twin pressure roller includinga stationary axle and two rotatably supported upper rollers, the holdingdevice comprising: at least one positioning element assigned to the axleof the twin pressure roller and at least one force transmission element,wherein the positioning element is arranged in a center area of the axleof the twin pressure roller and permits the twin pressure roller to movein a pendulum fashion around the center; wherein the holding device,together with the twin pressure roller are liftable from the bottomroller; and at least one catch bearing assigned to the twin pressureroller for approximate positioning of the twin pressure roller whenplaced on the bottom rollers.
 2. The holding device according to claim1, wherein the catch bearing is assigned to the axle of the twinpressure roller.
 3. The holding device according to claim 1, wherein atleast two catch bearings are arranged at a distance to one another andin close proximity to the upper rollers.
 4. The holding device accordingto claim 2, wherein at least two catch bearings are arranged at adistance to one another and in close proximity to the upper rollers. 5.The holding device according to claim 1, wherein the force transmissionelement is arranged separately from the positioning element.
 6. Theholding device according to claim 2, wherein the force transmissionelement is arranged separately from the positioning element.
 7. Theholding device according to claim 3, wherein the force transmissionelement is arranged separately from the positioning element.
 8. Theholding device according to claim 1, wherein the catch bearing isintegrated into the force transmission element.
 9. The holding deviceaccording to claim 5, wherein the force transmission element is arrangedseparately from the positioning element.
 10. The holding deviceaccording to claim 1, wherein the force transmission element isintegrated into the positioning element.
 11. The holding deviceaccording to claim 2, wherein the force transmission element isintegrated into the positioning element.
 12. The holding deviceaccording to claim 3, wherein the force transmission element isintegrated into the positioning element.